Container made of drawn glass

ABSTRACT

The invention relates to a container obtained by drawing, the container having a substantially cylindrical body and a neck that is provided, on going from its rim, both with an outside thread and with a ring of outside diameter that is substantially equal to the diameter at the crest of the thread, wherein the ring includes a middle groove.

The present invention relates to fabricating containers out of drawn glass.

BACKGROUND OF THE INVENTION

Fabricating containers out of drawn glass is a technique that is inexpensive, but that presents limits concerning the shapes that can be obtained. The simplest shape is a hollow cylinder like a test tube, and on departing from that shape, it is necessary to envisage implementing additional fabrication means that are more complex and that therefore naturally increase the cost of the product.

Furthermore, for containers that possess a worked neck, i.e. a neck comprising for example a ring surmounted by an outside thread, fabrication from drawn glass tubes is not appropriate. Starting from the segment of drawn tube, it is necessary to form an end mass of thickness greater than the thickness along the main portion of the wall of the container, with forming tooling associated with a mandrel then being used to make the required outside impressions therein. In known manner, starting from a tubular blank rotating about its axis, extra thickness is provided at one of its ends by progressively pushing it against an abutment surface. Thereafter, while the thickened glass is kept hot, the outside shapes in relief are formed by means of external forming tools, with a supporting mandrel being received in the blank where it has been thickened. Final cooling takes place while the container continues to rotate in air about its own longitudinal axis. In order to make a thread above the ring for the purpose of co-operating with conventional closure systems, it is necessary to soften a large mass of glass in which temperature does not become established uniformly, thereby harming subsequent forming operations. The tooling for shaping the outside portions in relief is then no longer suitable for performing its function in ideal manner and it is not unusual to find that 30% to 40% of containers are not in compliance and therefore constitute rejects, thus making the cost price of a container more expensive.

In practice, it is the container closure means that determine how the neck of the container is shaped, at least on its outside. The problem to be solved is thus how to take a drawn glass blank and fabricate a neck that is suitable for receiving conventional closure means. It is not conceivable to attempt to reduce the cost price of a container by requiring novel specific closure means to be developed since that would involve costs that are much greater than the savings achieved by the drawing technique. The closure means in question are those comprising a screw cap that is extended by a sleeve from which the cap is separable along a line of weakness.

OBJECT OF THE INVENTION

The present invention seeks to propose a solution for fabricating a container from a drawn glass blank in which the neck is shaped so as to accept a screw cap on a thread, together with a crimped sleeve under a ring that is surmounted by the thread.

DETAILED DESCRIPTION OF THE INVENTION

To this end, the invention provides a container comprising a body obtained by substantially cylindrical drawing and a neck that is provided, on going from its rim, both with an outside thread and with a ring of outside diameter that is substantially equal to the diameter at the crest of the thread, wherein the neck includes a middle groove.

This structural disposition for the container enables the entire container to be fabricated from a drawn glass blank.

The shape of the invention of the neck of the container has no effect on its outside dimensions and has no effect on its longitudinal size, and thus has no effect on the location and the axial size of the ring, which constitute values that are critical for receiving the closure of the container. Closure is very often provided by a metal cap that is fitted, while it is cylindrical in shape, on the neck, and that is then deformed from the outside so as to fit closely over the thread in its top portion close to the rim, against which it rests in sealed manner by means of a sealing element that is provided for this purpose in the end of the cap. Beyond the thread and a peripheral line of weakness, the cap is extended by a cylindrical sleeve that is crimped under the ring so as to create a shoulder that holds the cap in sealed contact against the rim of the neck and that retains the sleeve axially when the container is opened by unscrewing the top portion of the cap. The line of weakness can then break enabling the screw portion of the cap to be separated from the sleeve that remains secured to the container.

It will be understood that the presence of the outside groove formed in the surface of the ring has no effect on the quality of closure. In contrast, the presence of this groove makes it possible to reduce the quantity of the mass of glass that needs to be softened in order to thicken the wall, and thereby correspondingly reduces the risk of temperature non-uniformities that disturb the operations of the tools for shaping the neck. This reduces the reject rate and thus lowers the cost of manufacture.

Furthermore, the dimensions appropriate for making the closure on conventional machines with common caps are conserved. It can even be mentioned that the line of weakness of the cap can be situated over the groove so that it becomes possible to break the cap at the line of weakness without it being necessary to unscrew the top portion of the cap, the line of weakness being broken merely by pushing the zone that includes it into the setback of the groove. That makes it possible to remedy a drawback that is encountered very often with this type of closure as a result of the line of weakness being too strong. Under such circumstances, unscrewing the cap destroys the screw thread of the cap by turning it over the thread on the neck without allowing it to move axially, thereby, although not making it impossible to open the container, at least making it impossible to reuse the cap to provide temporary reclosure of the container while it is in use.

In a preferred embodiment of the invention, the width of the groove is equal to at least half its height, and the depth of the groove is of the same order as the thickness of the wall of the container.

Other characteristics and advantages of the invention appear from the description given below of an embodiment.

BRIEF DESCRIPTION OF THE DRAWING

Reference is made to the accompanying drawing, in which:

FIG. 1 is an outside view of a neck of a container in accordance with the invention; and

FIG. 2, in section, shows a neck fitted with closure means.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the neck of a container with a substantially cylindrical body 1, and in accordance with the invention. The body 1 is made of drawn glass and the neck 2 comprises two superposed sections. The top section 2 a adjacent to the rim 3 carries an outside thread 4 (having one or two threads) while the bottom section 2 b is formed by an outside ring 5 defining at least one bottom shoulder 6 and possessing a central groove 7. In the example shown in the figure, the depth of the groove is substantially equal to the mean thickness of the wall of the container, while the thickness of said wall at the bottom of the groove is also substantially equal to said value. The ring 5 is thus subdivided into two superposed rings 5 a and 5 b spaced apart by the groove 7. The volume of material located in said ring is much less than the volume in a conventional ring having the same dimensions. As a result a much smaller mass of glass is used in this location, thus making it possible during fabrication to shape the outside of the neck of the container in continuity with the drawing, without the neck becoming off-center relative to the body, as is observed to happen with a “solid” ring, as mentioned above.

In spite of its “lightweight” shape, the ring continues to perform the same functions as a conventional ring. As shown in FIG. 2, the container may be fitted with a conventional metal cap in conventional manner. The cap is in the form of a kind of bushing comprising a metal foil cylinder 10 having its end wall lined with a sealing coating 11, and that is itself shaped around the neck so as to fit closely over the thread 3 and the shoulder 6 by being deformed plastically, with sealing contact being provided at the rim of the neck. The cylindrical portion of the cap possesses a line of weakness 12, e.g. constituted by a series of perforations that are such that unscrewing the cap gives rise simultaneously to torque in shear on the sleeve and axial traction, which in combination cause the cap to become separated from the bottom portion of the cylindrical sleeve that remains on the neck, being retained by the shoulder 6. It should be observed that the line of weakness 12 is situated over the groove 7. This disposition is advantageous, since it is not unusual for the strength of the line of weakness to be too great for it to be broken. Under such conditions, the cap turns as a whole and its impression of the screw thread becomes destroyed, so that the unscrewing and axial traction that result therefrom are no longer produced. Opening the container then requires the cap to be destroyed by means of a knife, for example. Under such circumstances, with the ring of the invention, it suffices to push the sleeve in around the line of weakness in order to break it simply, and thus enable the cap to be separated. 

1. A container obtained by drawing, the container comprising a substantially cylindrical body and a neck that is provided, on going from its rim, both with an outside thread and with a ring of outside diameter that is substantially equal to the diameter at the crest of the thread, wherein the ring includes a middle groove.
 2. The container according to claim 1, wherein the width of the groove is equal to at least half its height.
 3. The container according claim 1, wherein the depth of the groove is of the same order as the thickness of the wall of the container.
 4. The container according claim 2, wherein the depth of the groove is of the same order as the thickness of the wall of the container. 